The term flame-retardant intumescent mixtures refers to foaming flame-retardant mixtures, in other words mixtures which foam to a certain extent upon exposure to fire and have flame-retardant properties.
Mixtures of this type may be used, for example, in joints in buildings and ruptures in cables, cavities, holes, transitions and connections in walls of buildings or fire safety components such as claddings to prevent the spread of the fire, conflagration gases and smoke in the event of fire. Components made of these mixtures are therefore used for preventive fire safety.
The expanding behaviour of these compounds in the event of fire can also make a particular contribution to the preservation of shape or function of, for example, ceiling and wall claddings, because the components are compressed by expanding profiles and sealing members.
These mixtures have to have further properties, for example water resistance. Therefore, conventional flame retardants such as water-soluble polyphosphates are usually undesirable. The extent of foaming also has to remain unchanged over very long storage times.
It is known from JP-B-95068362 to use expanded graphite as flame-retardant component in mixtures of vulcanised acrylate rubber. JP-B2-95103948 describes vulcanised acrylate rubber materials with expanded graphite for producing flame-retardant hoses.
Expanded graphite rubber mixtures based on polychloroprene with 30 phr (per hundred rubber) maximum expanded graphite and therefore excessively small proportions of this filler are described in JP-A-10036572. Furthermore, the use of halogen-containing components is undesirable nowadays.
JP-A-09176579 describes mixtures with EVA (10 to 50% VA) or m-PE with phosphorus and expanded graphite and mineral filler for adhesive tapes round pipes through wall apertures. Red phosphorus is invariably used. However, red phosphorus is difficult to process. In addition, red phosphorus may continue to react after processing.
The object of this invention was to find a phosphorus-free, in particular red phosphorus-free mixture which withstands the necessary fire safety tests, has adequate expanding behaviour, is waterproof and allows simple shaping, for example by extrusion, calendering, compression moulding, etc.
Furthermore, the shaped articles to be produced should have adequate dimensional stability but still be deformable to a certain extent, to still allow adaptation to the protective substrates or insertion into the joints in the component or building during construction and assembly.
A further object was to avoid the need for further vulcanisation or maturing periods to enable the article to be used immediately after shaping. A further object was accordingly to provide unvulcanised mixtures having adequate stability of shape while being deformable to a certain extent by the user.
In addition, it was desired to use substantially halogen-free feedstock for producing these mixtures.